Thermoplastic blanket materials are well known in the art and are used in a variety of settings where it is desired to dampen noise from an external source. For example, thermoplastic blanket materials have been used in applications such as in appliances to reduce the sound emitted into the surrounding areas of a home, in automobiles to reduce mechanical sounds of the motor and road noise, and in office buildings to attenuate sound generated from the workplace, such as from telephone conversations or from the operation of office equipment. Acoustical insulation materials typically relies upon both sound absorption (i.e., the ability to absorb incident sound waves) and transmission loss (i.e., the ability to reflect incident sound waves) to provide adequate sound attenuation.
Conventional acoustical insulation materials include materials such as foams, compressed fibers, fiberglass batts, felts, and nonwoven webs of fibers such as meltblown fibers. Laminates formed of one or more layers of the thermoplastic blanket materials provide the desired acoustical and insulating properties and one or more additional layers of a rigid material provide desired mechanical strength properties and permit simple and convenient installation as well as proper functional performance. Such thermoplastic blanket materials may be used in the walls of single family homes and commercial buildings to both insulate and reduce sound emission from the rooms.
Relatively higher density board products produced from thermoplastic blanket materials may be utilized as structural parts for appliances, office screen partitions, in hood liners, head liners, and in other automotive and truck applications. An example of such a densified board formed from a thermoplastic blanket material is described in U.S. Ser. No. 2004/0265553 and U.S. Ser. No. 2005/0136235 to Rockwell, et al. In these applications, a thermoplastic blanket is densified on at least one surface by passing the insulation blanket between two or more heated platens. Heat and pressure is applied to the insulation blanket by the platens to form a densified surface having a desired thickness. After heating the insulation blanket, the densified blanket may then be cooled, such as by passing the densified blanket between cooling platens.
Although densified forms of thermoplastic blanket materials exist, there remains a need in the art for a method of forming a densified thermoplastic product that allows for a reduction in heating time, more homogenous heating throughout the thermoplastic product, and a stiffer final product.